The invention relates to a ceramic honeycomb composite structure and more particularly a new and improved ceramic honeycomb composite structure, a catalyst supported thereby and a method of producing the same wherein the composite structure is further provided thereon with active material layers onto which is applied catalytic component to form the catalyst.
Various methods have been known for producing ceramic honeycomb structures having useful applications as catalyst supports. Typical of them is the extrusion method using a die through which ceramic material is extruded to form the honeycomb structure. In other typical method, corrugated flexible ceramic green sheets are laminated or piled and then sintered to form the honeycomb structure.
The support for a catalyst used for purifying, for example, an outlet exhaust gas from an internal combustion engine mounted on a motor vehicle is required to have not only a high mechanical strength but also a sufficient catalyst-supporting property which greatly affect a possible durability of the catalyst. However, it is in effect difficult to obtain such a catalyst which has a high mechanical strength and a sufficient catalyst-supporting property, because a catalyst support which is of high density for the purpose of increasing its mechanical strength has only a poor catalyst-supporting property owing to its smooth surfaces. On the other hand a catalyst support which is of low density for the purpose of increasing its catalyst-supporting property has generally only a low mechanical strength. Particularly, a catalyst support made in the extrusion method which is useful to obtain ceramic honeycomb structures inherently exhibits a grain orientation in the surfaces in parallel with its extruded direction to provide smooth surfaces resulting in a poor catalyst-supporting property.